1. Field of the Invention
This invention relates to brake boosters for vehicles and more particularly to a tandem diaphragm brake booster of the type used in association with a vehicle brake system. In a vehicle brake system, the space for provision of a brake booster is severely restricted, especially in the radial direction of the vehicle body as compared to the longitudinal direction thereof. In order to save space in such radial direction, a tandem type diaphragm brake booster has been frequently used.
2. Description of the Prior Art
Conventionally, as is shown in U.S. Pat. No. 3,603,208, first and second diaphragms in such a tandem diaphragm booster arrangement are secured by bolts and nuts 50, 52. This connection is very difficult in manufacturing and necessitates the use of bolts and nuts, as indicated, which will of course increase the manufacturing cost. Further, a key member (not numbered, but appearing in FIG. 1 of the U.S. Patent) is disposed between two portions 38 and 40 of a hub 42 for preventing a valve means 76 from returning during valve operation.